Generally, a conical crusher is comprised of a head assembly including a conical crusher head which gyrates about a vertical axis by means of an eccentric mechanism. The eccentric mechanism is driven by any one of a number of power drives such as diesel engines or electrical motors. The exterior of the conical head is covered by a wearing mantle which engages the material being crushed. Spaced circumferentially around the head assembly and fixed to a stationary frame of the crusher is a bowl fitted with a bowl liner. The bowl liner provides an opposing surface for the mantle during the crushing operation.
Typically, the opposing surfaces of the mantle and bowl liner form a downwardly tapering crushing cavity which is generally V-shaped in cross-section. Such an arrangement is disclosed in commonly assigned U.S. Pat. No. 4,750,681. The width of this cavity at the crusher setting, or narrowest point between the bowl liner and the head, determines the maximum particle size in the crushed material.
Conical crushers contain components such as bearings, shafts, seals, bushings and other devices for permitting relative movement between working parts which enable the rock crushing operation. Some working parts are particularly subject to severe operating conditions and require periodic maintenance and replacement. One such part is the thrust bearing used for supporting the eccentric mechanism for rotation about the vertical axis.
In conical crushers of the type used to employ this invention, an upper bearing and a lower bearing are configured for concentric, sliding engagement with each other, thus forming a thrust bearing assembly or system. The two bearings can be made of the same metal, such as steel or bronze, or they can be made of different metals, such as one steel and the other bronze. The lower bearing is fixed to the stationary frame of the rock crusher, and the upper bearing is fixed to the eccentric mechanism. The lower bearing is provided with a generally uninterrupted wearing surface or race on which the upper bearing rides. The upper bearing has a number of channels or grooves leading from an inner edge of the bearing across the wearing surface to an outer edge of the bearing for providing lubrication to the wearing surfaces of the upper and lower bearings.
Various lubrication groove configurations are known in the art. An upper thrust bearing 20, shown in prior art FIGS. 1 and 2, includes a plurality of grooves 21 in a known groove configuration. Bearing 20 is used in the NORDBERG MP 1000 line of rock crushers. Each groove 21 of bearing 20 requires several milling or machining operations. In particular, a central cut 22 is made at a depth of about 18 millimeters extending across an annular wearing surface 24 of bearing 20 from an inner wall 26 to within about 10 millimeters of an outer wall 28. In another machining operation, a bleed hole 25 is made in each groove 21 at about 5 millimeters off the bottom of groove 21 extending from the outer end of cut 22 to outer wall 28 of bearing 20. Bleed hole 25 allows excess lubrication to exit groove 21 which in turn allows fresh lubrication to enter groove 21. Thus, bleed hole 25 prevents excess heat in bearing 20 as a result of pooling of heated lubrication. In yet another machining operation, a shallow ramp 30 is milled across wearing surface 24 adjacent the rotationally trailing edge of cut 22. In addition to the expense of multiple milling operations, bearing 20 has another drawback in that ramp 30 is so shallow that it wears out relatively quickly, and thus requires frequent replacement. In particular, ramp 30 is only about 0.2 millimeters deep at points immediately adjacent cut 22. Thus, with bearing 20 having a total thickness of about 45 millimeters, bearing 20 requires replacement when only about 0.5% of the thickness of bearing 20 has been worn away. An additional expense in manufacturing bearing 20 results from bearing 20 having a separate annular mounting ring 34 for locating bolt holes 36, adding to the material costs.
Replacing worn thrust bearings is particularly time consuming because the crusher must be dismantled and then reassembled, which on a typical crusher may require from 50 to 100 man hours. Further, replacing these bearings is costly due to high material cost associated with the bearings, which often have very large diameters. For example, bearing 20 of the MP100 rock crusher has an outer diameter of 1090 millimeters (or, about 3'7").
An upper thrust bearing 40, shown in prior art FIGS. 3 and 4, includes a plurality of grooves 41 in another known groove configuration. Bearing 40 is used in the NORDBERG WF800 and HP700 lines of rock crushers. Each groove 41 of bearing 40 includes a central cut 42 having a depth of about 13 millimeters, but which is otherwise similar to central cut 22 of bearing 20 described with respect to FIGS. 1 and 2. However, unlike ramp 30 of bearing 20, a ramp 44 in bearing 40 is relatively deeper. In particular, ramp 44 has a depth of about 4.7 millimeters adjacent a trailing edge 47 of cut 42 and a maximum depth of about 8.0 millimeters along an outer wall 45 as shown at 49. The increased depth of ramp 44 eliminates the need for a separate bleed hole for groove 41 and, at the same time, increases the service life of bearing 40. Also, with bolt holes 46 positioned directly on a wearing surface 48 of bearing 40, no extra material is required for a separate mounting ring, reducing material costs. On the other hand, with bolt holes 46 so positioned, wearing surface 48 between grooves 41 is interrupted by bolt holes 46. A further disadvantage of this groove configuration is that at least two machining operations are required to make each groove 41. In particular, central cut 42 requires a machining operation and ramp 44 requires another machining operation.
Upper thrust bearings 60 and 70, shown in prior art FIGS. 5-6 and 7-8, respectively, each include a plurality of grooves 61 and 71, respectively, in additional known groove configurations. Bearing 60 is used in the NORDBERG HP500 line of rock crushers and bearing 70 is used in the NORDBERG 1560 OMNICONE line of rock crushers. Each groove 61 of bearing 60 includes a central, semi-circular cut 62 having a radius of about 13 millimeters and a depth of about 11 millimeters. Additionally, each groove 61 includes a ramp 64 extending from a trailing edge of cut 62 to a wearing surface 66. Each groove 71 of bearing 70 is basically the same as groove 61 in bearing 60, except that groove 71 has a pair of ramps 72, 76 adjacent a central, semi-circular cut 74, instead of just the one ramp 64 of groove 61. Thus, whereas each groove 61 in bearing 60 requires at least two machining operations, each groove 71 in bearing 70 requires at least three machining operations. In particular, each groove 61 requires a machining operation for central cut 62 and another machining operation for ramp 64; and each groove 71 requires a machining operation for central cut 74, another machining operation for ramp 72, and yet another machining operation for ramp 76.
Thrust bearings are costly to manufacture because of the expensive machinery required. Therefore, elimination of one or more machining steps would lead to increased efficiencies for operating these machines, thus reducing the costs of producing bearings.
Thus, there is a need for a thrust bearing for a conical crusher having a wearing surface configured to allow continued service life even when significant erosion of the wearing surface has taken place. There is also a need for a thrust bearing which provides an uninterrupted contact area between the lubrication grooves of the wearing surface. There is further a need for a thrust bearing for a conical crusher which is less expensive to manufacture.